X0306 4 2017-12-11 0 0001503274 Quanterix Corp QTRX 0001216068 DEKKERS MARIJN E C/O QUANTERIX CORPORATION, 113 HARTWELL AVENUE LEXINGTON MA 02421 1 0 0 0 Common Stock 2017-12-11 4 C 0 77378 A 77378 D Series D-1 Preferred Stock 2017-12-11 4 C 0 248694 D Common Stock 77378 0 D The shares of preferred stock automatically converted into common stock immediately prior to the closing of the Issuer's initial public offering using a calculation defined in the Issuer's Restated Certificate of Incorporation, as amended, based on the initial purchase price and the conversion rate in effect at the time of conversion. The shares of preferred stock automatically converted on a 1-for-3.214 basis and such conversion rate is reflected in the amount of common stock underlying the security. These shares were convertible into the Issuer's common stock in accordance with the Issuer's Restated Certificate of Incorporation, as amended, at any time after the issuance of such shares, at the holder's election. Not applicable. /s/ Brian Keane, as Attorney-in-Fact 2017-12-11